Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, an information processing apparatus, a control method thereof, and a non-transitory computer-readable medium and, more particularly, to color matching processing of converting an image signal of data described in a page description language into a signal in the color space of an output apparatus.
Description of the Related Art
Color space conversion (color matching) processing using color space information of an image signal and color space information of an output apparatus such as a printer is performed to convert an image signal of input data described in the page description language into a signal in the color space of the output apparatus. The color space information of the image signal includes a calculation equation for converting an image signal into a device-independent uniform color space (for example, a CIE-XYZ color space defined by Commission Internationale de l'Eclairage). The color space information of the output apparatus includes a calculation equation for converting a signal in the uniform color space into a signal in the color space of the output apparatus. By using these two pieces of information, the output apparatus converts an image signal into a signal in the color space of the output apparatus through the uniform color space.
However, the calculation equation is not directly used in actual conversion, and conversion is performed by interpolation calculation using a lookup table in which only the calculation results of some input signals are stored. This is because the calculation equation of color space information is generally complicated and processing takes time. However, in a method using the lookup table, when important colors (to be referred to as primary colors hereinafter) such as white, red, green, and blue do not coincide with the grid points of the lookup table, the values of the primary colors need to be calculated by interpolation calculation based on the grid points of colors other than pure colors. As a result, the quality of an image output by the output apparatus becomes poor. To solve this, Japanese Patent No. 5025323 discloses a method of assigning pure colors in an sRGB standard color space to grid points.
However, in the technique disclosed in Japanese Patent No. 5025323, primary colors cannot be assigned to grid points for image data of the page description language in which color space information other than standard one is described, thus degrading the image quality.